March 11 (Bloomberg) -- With few clues about what happened
to a missing Malaysian wide-body plane or even where it is,
aviation investigators and security analysts are left with one
conclusion: almost no theory can be considered off the table.

Hijacking, terrorist attack, pilot suicide, mechanical
failure, a flight-crew miscue or another unforeseen issue all
may have brought down the Boeing Co. 777-200 somewhere between
Malaysia and Vietnam, five experts said in interviews.

Because it’s so improbable a plane the size of a 777,
Boeing’s biggest twin-engine jet, would just disappear or land
somewhere undetected by modern technology, searchers probably
are looking in the wrong places, said Michael Barr, who teaches
aviation accident investigation at the University of Southern
California.

“That’s what’s surprising to me,” Barr said. “Everybody
is chasing their tail. There isn’t a lack of debris. There’s a
lack of knowledge where the debris field is.”

Malaysian Airline System Bhd. Flight 370 went missing March
8 en route to Beijing from Kuala Lumpur with 239 people aboard.
So far, searchers haven’t turned up any confirmed wreckage and
even information on its last known position has been vague.

Many Scenarios

Airliners that have gone missing or crashed from higher
altitudes since the dawn of the jet age in the 1950s can be
grouped into a handful of categories, Steve Wallace, former head
of the U.S. Federal Aviation Administration’s accident
investigation arm, said in an interview.

They include structural failures, criminal or terrorist
acts, a fuel tank explosion and pilot errors, often in
combination with malfunctions, Wallace said.

“At the outset of the investigation, everything is on the
table,” he said.

A hijacking scenario could explain why the 777’s remains
haven’t been found, he said. If terrorists or criminals were
able to get past the hardened cockpit doors adopted
internationally after the Sept. 11, 2001, terrorist attacks in
New York, they may have forced pilots to change course or to
switch off the transponder beacon that makes the plane easier to
track by radar.

Shoe Bombs

Kip Hawley, a former administrator of the Transportation
Security Administration, said he was concerned that terrorists
may have smuggled explosives onto the flight in their shoes.

Airlines were warned by the U.S. Department of Homeland
Security in mid-February of credible threats about shoe bombs,
which Richard C. Reid, a self-declared al-Qaeda member, used in
an unsuccessful attempt to blow up an American Airlines jet en
route to Miami from Paris in 2001.

Such a device, depending on its components and power, could
bring down a large plane, Hawley said in an interview.

The North American Air Defense Command’s early warning
system detected no anomalies relating to the Malaysian airline
incident, said a command official in Colorado Springs, Colorado,
speaking on the condition of anonymity to discuss intelligence
activities.

U.S. intelligence agencies have detected no burst of
chatter on airwaves or online that’s characteristic of what
often follows a terrorist attack, a U.S. intelligence official
said, also speaking on the condition of anonymity.

Increases in calls and messages to and from Malaysia and
countries that had passengers on the flight can be attributed to
communications involving people seeking news of the fate of
their loved ones, the official said.

Investigations Started

Still, the fact that two passengers were carrying stolen
passports raises a red flag, John Magaw, a former administrator
of TSA and a former director of the U.S. Secret Service, said in
an interview. Austria and Italy said the passports were stolen
from their nationals.

Authorities have almost certainly begun a terror
investigation in the event that’s what brought down the plane,
Richard Marquise, a former FBI agent who was the lead criminal
investigator on the bombing of Pan Am Flight 103 over Lockerbie,
Scotland, in 1988, said in an interview.

They are probably checking the backgrounds of passengers,
crew members and anyone else who may have come in contact with
the aircraft to see if they have any connections to terrorism,
Marquise said. Even if the plane isn’t recovered, they may be
able to trace someone to a terror network or to explosives, he
said.

“At this stage of the investigation, when you have
absolutely zero evidence of anything, you have to make an
assumption that it was catastrophic and it could well have been
terrorism or a criminal act,” he said.

Debris Field

A mid-air explosion that destroyed a jetliner would create
a large debris field, John Hansman, a professor of aeronautics
and astronautics at the Massachusetts Institute of Technology,
said in an interview.

“If it was a bomb, why aren’t you finding pieces of the
plane scattered all over the place?” Hansman said.

The size and visibility of any wreckage may vary widely
depending on factors including wind speed and direction at
multiple altitudes, the weight and shape of objects, the type
and location of the explosive, whether debris fell on land or in
water and, if the latter, the direction of currents and force of
waves.

In previous accident investigations, agencies such as the
U.S. National Transportation Safety Board performed analyses to
estimate where debris will fall.

One explanation for the plane’s loss is a failure no one
has seen before, Thomas Haueter, former chief aviation
investigator at NTSB, said in an interview. As causes of
accidents have been gradually eliminated by safety improvements,
such crashes have become the norm, he said.

Something New

That was the case in the loss of Air France Flight 447,
which went down in the Atlantic Ocean on June 1, 2009, killing
all 228 aboard, Haueter said. The plane encountered a high-altitude storm that caused the pilots’ airspeed indicators to
malfunction after ice formed in them.

The pilots, in the resulting confusion, let the jetliner
slow to the point it went into an aerodynamic stall and crashed
in water about 3,900 meters deep. It took searchers almost two
years to find the wreckage on the ocean floor.

One issue that hasn’t been answered about the Malaysian
plane is what kind of communication equipment it had aboard that
would help find the wreckage.

Telemetry Question

Some 777s are programmed to automatically radio data about
the engines and other equipment during flight. Those telemetry
broadcasts include a plane’s location and that information was
used to help find the Air France Airbus Group NV A330 in the
Atlantic. Officials from Malaysian and Boeing haven’t said
whether the plane had such equipment.

“In cases like this, where you have an airplane go down in
the water, it’s not unusual to have a period where you are
searching and don’t know where it is yet,” Hansman said. “This
is the normal phase of this process. Everybody wants to have an
answer right away. It takes a while to find the evidence.”